cat terrified of other cat after being spayed

I have two cat who were best friends. One is a male and the other a female. Recently the female was spayed and ever since the male has hissed and "screamed" everytime he sees her. This has not gotten better with time.

I have been thruogh this. It's quite disturbing, however they are indeed cats and they will take thier sweet time. May never get over it , but the aggression usually subsides as they eventually become bored and move on